package org.apache.lucene.util.fst;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import org.apache.lucene.store.DataInput;
import org.apache.lucene.store.DataOutput;

/**
 * Pairs up two outputs into one.
 *
 * @lucene.experimental
 */

public class PairOutputs<A, B> extends Outputs<PairOutputs.Pair<A, B>> {

    private final Pair<A, B> NO_OUTPUT;
    private final Outputs<A> outputs1;
    private final Outputs<B> outputs2;

    public static class Pair<A, B> {
        public final A output1;
        public final B output2;

        public Pair(A output1, B output2) {
            this.output1 = output1;
            this.output2 = output2;
        }

        @Override
        @SuppressWarnings("rawtypes")
        public boolean equals(Object other) {
            if (other == this) {
                return true;
            } else if (other instanceof Pair) {
                Pair pair = (Pair) other;
                return output1.equals(pair.output1) && output2.equals(pair.output2);
            } else {
                return false;
            }
        }

        @Override
        public int hashCode() {
            return output1.hashCode() + output2.hashCode();
        }
    };

    public PairOutputs(Outputs<A> outputs1, Outputs<B> outputs2) {
        this.outputs1 = outputs1;
        this.outputs2 = outputs2;
        NO_OUTPUT = new Pair<A, B>(outputs1.getNoOutput(), outputs2.getNoOutput());
    }

    public Pair<A, B> get(A output1, B output2) {
        if (output1 == outputs1.getNoOutput() && output2 == outputs2.getNoOutput()) {
            return NO_OUTPUT;
        } else {
            return new Pair<A, B>(output1, output2);
        }
    }

    @Override
    public Pair<A, B> common(Pair<A, B> pair1, Pair<A, B> pair2) {
        return get(outputs1.common(pair1.output1, pair2.output1), outputs2.common(pair1.output2, pair2.output2));
    }

    @Override
    public Pair<A, B> subtract(Pair<A, B> output, Pair<A, B> inc) {
        return get(outputs1.subtract(output.output1, inc.output1), outputs2.subtract(output.output2, inc.output2));
    }

    @Override
    public Pair<A, B> add(Pair<A, B> prefix, Pair<A, B> output) {
        return get(outputs1.add(prefix.output1, output.output1), outputs2.add(prefix.output2, output.output2));
    }

    @Override
    public void write(Pair<A, B> output, DataOutput writer) throws IOException {
        outputs1.write(output.output1, writer);
        outputs2.write(output.output2, writer);
    }

    @Override
    public Pair<A, B> read(DataInput in) throws IOException {
        A output1 = outputs1.read(in);
        B output2 = outputs2.read(in);
        return get(output1, output2);
    }

    @Override
    public Pair<A, B> getNoOutput() {
        return NO_OUTPUT;
    }

    @Override
    public String outputToString(Pair<A, B> output) {
        return "<pair:" + outputs1.outputToString(output.output1) + "," + outputs2.outputToString(output.output2) + ">";
    }
}
